You're on a long run and half way through want to check your electrolyte levels. Or you take a powerful cholesterol lowering drug and need a regular liver enzyme test. Wouldn't it be great if you had a portable lab – like diabetics with their blood glucose meters?

Except, the latest invention is a lab on paper the size of a stamp. Dr. George Whitesides of Harvard University says paper tests aren't new because for decades women have used pregnancy tests. But unlike the stick, his "stamp-lab" can detect complex diseases instantly at a penny a piece, and like the home pregnancy test, do it reliably without a doctor to interpret the results.

Whitesides uses microfluidics, which is the science of moving fluids on a tiny scale. Surprisingly, his paper test isn't made with much more than filter paper and an office printer.

A modified printer can copy over one hundred patterns per sheet using melted black wax. The dried patterns become channels that guide fluid samples along the test strip. In these channels chemicals are applied which react in the presence of specific biological substances.

One particular test detects aspartate transaminase or AST, which is released by dying liver cells. As a drop of blood is applied to the test strip, an outer membrane allows only plasma through.

Several pieces of the test paper are actually stacked and taped, so when the plasma enters the second layer and mixes with chemicals there, a reaction takes place if AST is present. If so, the third layer containing a normally blue dye, turns colorless – testing positive for liver damage.

This test is aimed at the millions of Africans whose drug therapies for AIDS and tuberculosis can damage the liver. But, once the tests can diagnose everything from malaria to maybe even cancer, people won't have to wait until they're too sick before seeing the doctor.

For more information…

George Whitesides: A lab the size of a postage stamp [Video]
George Whitesides discussed his research at the TEDxBoston conference, where this "TED Talks" video was recorded. From the TED description: "Traditional lab tests for disease diagnosis can be too expensive and cumbersome for the regions most in need. George Whitesides' ingenious answer, at TEDxBoston, is a foolproof tool that can be manufactured at virtually zero cost."

Far From Any Lab, Paper Bits Find IllnessThe
New York Times published this article on Dr. Whitesides' research as part of its "Small Fixes" special section on low-cost innovations that can save thousands of lives.

The Nonprofit 'Diagnostics For All' Provides a Lesson For Us All
Dr. Whitesides took his technology and founded the non-profit Diagnostics For All, which is dedicated to providing low-cost, easy-to-use diagnostics for the 60% of the developing world which doesn't have access to hospitals or medical facilities. From this editorial at Genetic Engineering & Biotechnology News: "[...] perhaps the greatest demonstration of intelligence is not in the technology itself, but rather what Dr. Whitesides decided to do with it."